Administering an injection is a process which presents a number of risks and challenges for users and healthcare professionals, both mental and physical.
Injection devices (i.e. devices capable of delivering medicaments from a medication container) typically fall into two categories—manual devices and auto-injectors.
In a manual device—the user must provide the mechanical energy to drive the fluid through the needle. This is typically done by some form of button/plunger that has to be continuously pressed by the user during the injection. There are numerous disadvantages to the user from this approach. If the user stops pressing the button/plunger then the injection will also stop. This means that the user can deliver an underdose if the device is not used properly (i.e. the plunger is not fully pressed to its end position). Injection forces may be too high for the user, in particular if the patient is elderly or has dexterity problems.
The extension of the button/plunger may be too great. Thus it can be inconvenient for the user to reach a fully extended button. The combination of injection force and button extension can cause trembling/shaking of the hand which in turn increases discomfort as the inserted needle moves.
Auto-injector devices aim to make self-administration of injected therapies easier for patients. Current therapies delivered by means of self-administered injections include drugs for diabetes (both insulin and newer GLP-1 class drugs), migraine, hormone therapies, anticoagulants etc.
Auto-injectors are devices which completely or partially replace activities involved in parenteral drug delivery from standard syringes. These activities may include removal of a protective syringe cap, insertion of a needle into a patient's skin, injection of the medicament, removal of the needle, shielding of the needle and preventing reuse of the device. This overcomes many of the disadvantages of manual devices. Injection forces/button extension, hand-shaking and the likelihood of delivering an incomplete dose are reduced. Triggering may be performed by numerous means, for example a trigger button or the action of the needle reaching its injection depth. In some devices the energy to deliver the fluid is provided by a spring.
It may be desirable to provide the user of the auto-injector with a feedback about the current state of the auto-injector, for example to inform them that the dose of drug was fully delivered so they can remove the auto-injector from the injection site.
WO 2005/115509 A1 discloses an injection device comprising:                a housing adapted to receive a syringe having a discharge nozzle,        the housing having an indicator opening;        a forward drive arranged to act upon the syringe on actuation to advance the syringe from a retracted position to an extended position thereby discharging the contents of the syringe through the discharge nozzle;        a return drive arranged to act upon the syringe after the contents of the syringe have been discharged to withdraw the syringe from the extended position to the retracted position.        
The return drive is arranged in the housing so that it does not obscure an inspection of the contents of the syringe through the indicator opening.
WO 2009/141650 A2 discloses an autoinjector provided with a magnetically operated “injection complete” indicator. A moveable magnet associated with the drive piston is kept at one end of a recess by a soft iron keeper until the drive piston reaches its formal position where the moveable magnet is attracted to impact a magnet on the housing to generate an audible click. Also described is a spring finger that slips behind the rear edge of the syringe boot temporarily to hold the end of the boot well clear of the housing to that it can be gripped for removal.
DE 10 2004 052 219 A1 discloses an injection device comprising a signal generation that exhibits a minimum trigger level, in which the signal is not induced by deforming contact of the releasing element and shifting mechanics within a housing, where the strength of the signal is independent of the energy strength and/or duration of the effective energy and the place element exhibits covering by fluid or electronic signal generation equipment.
WO 2006/134153 A1 discloses a manual injection pen suitable for injecting a liquid medication via a non-electrical drive mechanism. The injection pen is provided with a plurality of sensors that sense when a user is taking a specific action with the device. Further the injection pen is provided with a sound generator that generates a particular sound corresponding to the specific action taken by the user. In this way a characteristic sound signal can be provided for each specific action.
WO 2008/083875 A1 relates to a medical delivery device comprising a housing; a container containing medicament arranged inside the housing; a medicament delivery means in communication with the housing and capable of delivering medicament to a patient; force means capable of acting inside the container for delivering medicament during a certain time period via the medicament delivery means; mechanical information means acting in response to the force means; wherein said mechanical information means comprises vibrating means having at least one unbalance member capable of causing a vibrating sensation to the housing for providing tactile information to a patient during the time period, indicating medicament delivery.